In the container-making industry, containers are typically manufactured in at least two parts: a container body and at least one container end. The container body may be drawn and ironed such that only a single container end is required (two-piece container), or the container body may be formed by rolling a stamped sheet into cylindrical form and welding the seam such that two container ends are required (three-piece container). Regardless of the particular container structure, container manufacturers typically separately supply large quantities of container bodies and container ends to customers who introduce substances into the container bodies and subsequently attach the container ends to the container bodies.
In this regard, a predetermined number or "stick" of container ends can be packaged by the manufacturer in face-to-face relation in cylindrical bags having a diameter slightly greater than the container ends for shipment to the customer. A method and apparatus for bagging container ends is disclosed in co-pending, commonly-assigned U.S. patent application Ser. No. 08/023,341.
More recently, container ends have also been supplied to customers as unbagged sticks loaded into reusable trays. The filled trays are typically stacked on top of each other on a pallet, and the pallet is subsequently wrapped in clear plastic wrap to provide a contaminant barrier for the unbagged ends. The stacks of trays are then shipped to customers for use in can filling operations. The use of unbagged sticks of container ends and reusable trays eliminates the process of bagging and unbagging container ends and reduces paper waste (i.e., wasted bags).
The tray loading and palletizing process is generally initiated by receiving a continuous array of container ends from a conversion press via one or more troughs. The ends in each trough are counted and separated into sticks of container ends and each stick is subsequently removed from the trough and inserted into one of a number of appropriately-sized channels in the tray. When a tray is full, the process of loading trays starts again with a new tray. Filled trays are stacked onto a pallet to form a stack of trays, which is subsequently transported (e.g., by a forklift and ground transport) to a can filling station where the ends can be unloaded in a manner similar to, but in the opposite order of, the loading process described above.
Although some devices have been developed which have contributed to the automation of tray loading and palletizing, many of these devices tend to be space-consuming, expensive to operate, and/or unnecessarily complex due to the large number of component parts. In addition, such palletizers typically require the loading of the trays in a loading area separate from the stacking area and/or require a vertically-adjustable platform for iteratively maintaining the top of the stack at a constant height. Furthermore, such devices do not provide a means whereby multiple conversion presses may be serviced by a single apparatus while maintaining container ends from different presses physically separate from each other (e.g., on separate trays and pallets) for quality control purposes. Additionally, such devices typically do not provide a single apparatus which can provide the dual functions of transporting sticks and stacking trays.
Consequently, it is an object of the present invention to provide a reliable, low cost, automated palletizer. It is a related object of the present invention to reduce the number of components parts, to decrease the overall size of an automated palletizer, and to reduce pallet handling. Additionally, it is an object to provide a palletizer which can load sticks directly into a tray while the tray is stacked on other trays and to create a stack of trays without having to iteratively adjust the height of the top of the stack. Furthermore, it is an object of the present invention to provide a single device which can service multiple conversion presses and which can maintain container ends from different presses physically separate from each other.